1. Field of the Invention
The present invention relates to a manually-operated optical rotary encoder provided with a light receiving and emitting element, and particularly to an optical rotary encoder for producing a plurality of pulse signals.
2. Description of the Prior Art
Optical encoders for supplying pulse signals by manual operation are disclosed in U.S. Pat. No. 4,387,374 invented by Alan I. Wiener.
The structure for detecting a rotation of a reflecting plate is disclosed in U.S. Pat. No. 4,502,045 invented by Ingrid Fromn.
In addition, the structure for rotating two code plates around a common axis is disclosed in U.S. Pat. No. 3,912,926.
Manually-operated optical rotary encoders which need to be improved will be described with reference to FIGS. 12 through 22.
First, a first apparatus which needs to be improved will be disclosed in FIGS. 12 to 14, in which FIG. 12 is a partly sectioned plan view of a conventional optical rotary encoder, FIG. 13 is a sectional view and FIG. 14 illustrates in section the positional relationship between light reflecting portions of a first code plate and a second code plate. In FIG. 13, reference numeral 1 designates a substrate for wiring of a circuit, 2 a light receiving and emitting element mounted on the substrate 1, and A a first code plate, wherein a shield coating 4 is print-formed on the upper surface of a metal plate 3. Two patterns, which consist of a portion not coated with the coating 4 or a light reflecting portion and a portion coated with the coating 4 or a non-reflecting portion 6, are peripherally, alternately and continuously formed. Reference character B designates a second code plate, in which a shield coating 8 is formed on the upper surface of a metal plate 7 in the procedure similar to that of the first code plate A, and two patterns consisting of a light reflecting portion 9 and a non-reflecting portion 10 are peripherally, alternately and continuously formed. Reference numeral 11 designates a light travelling hole formed in the first code plate A, 12 an outer shaft for rotating and driving the first code plate A, and 13 an inner shaft for rotating and driving the second code plate B, the outer shaft 12 and the inner shaft 13 constituting a dual shaft. Reference numeral 14 designates a bearing and 15 a casing.
When the outer shaft 12 is rotated, light emitted from the light receiving and emitting elements 2 is reflected by tbe light reflecting portions 5 of the first code plate A or absorbed by the non-reflecting portions 6 to thereby obtain pulse signals as desired from the elements 2 accordingly.
The inner shaft 13 is rotated with the light travelling holes 11 of the first code plate A opposed to the elements 2, and the light emitted from the elements 2 is reflected by the light reflecting portions 9 of the second code plate B or absorbed by the non-reflecting portions 10 to thereby obtain pulse signals as desired from the elements 2 accordingly.
Next, a second and a third apparatus which need be improved will be disclosed in FIGS. 15 to 22, in which FIG. 15 is an exploded perspective view showing the whole structure, FIG. 16 is a plan view showing the state wherein a code plate and a circuit substrate are arranged in correspondence to each other, FIG. 17 illustrates a click mechanism, FIG. 18 is an exploded perspective view showing a roller and a supporting member which constitute the click mechanism, FIG. 19 shows the reverse side of the first code plate, and FIG. 20 shows the reverse side of the second code plate.
In FIG. 15, reference numeral 1 designates a cover which forms a shell, 2 and 3 a first code plate and a second code plate, respectively, arranged relatively rotatably and coaxially opposedly, 4 an inner shaft secured to the first code plate 2, and 5 an outer shaft secured to the second code plate 3, the inner shaft 4 being rotatably arranged within the outer shaft 5. As shown in FIGS. 16 and 19, the first code plate 2 has a surface opposed to the second code plate 3, said surface being peripherally and alternately formed with reflecting portions 6 and non-reflecting portions 7 colored in black, with concave portions 8 and convex portions 9 formed in the outer peripheral edge. As shown in FIGS. 16 and 20, the second code plate 3 has, at positions corresponding to the reflecting portions 6 and non-reflecting portions 7 of the first code plate 2, through-holes or a first window 10 and a second window 11 having the size generally equal to that of the reflecting portions 6, as well as a reflecting window 12 formed of metal. Furthermore, reflecting portions 13 made of metal and non-reflecting portions 14 colored in black are provided peripherally including the first window 10 and the second window 11, and a heart-shaped grooved cam 15 is provided.
A first, a second and a third light receiving and emitting elements 16, 17 and 18 are arranged opposedly to the first window 10, the second window 11 and the reflecting window 12, respectively, of the second code plate 3. Reference numeral 19 designates a retainer for retaining these light receiving and emitting elements 16, 17 and 18, and 20 denotes a slider slidably mounted on the retainer 19, said slider having a square through hole 21. The slider 20 is provided on the upper portion thereof with a pin 22 which engages the edge of a grooved cam 15 of the second code plate 3. A spring indicated at 23 has one end attached to the retainer 19 and the other end attached to the slider 20 to urge the pin 22 so that the latter may engage with the end 24 of the grooved cam 15 shown in FIG. 4.
A circuit substrate 25 indicated at 25 in FIG. 15 having the retainer 19 mounted thereon is formed in the central portion thereof with a hole 26 into which the inner shaft 4 of the first code plate 2 and the outer shaft 5 of the second code plate 3 are rotatably inserted. 1n FlG. 15, reference numeral 27 designates a roller formed for example of rubber, which engages the concave portion 8 and convex portion 9 of the first code plate 2, 28 a supporting portion for rotatably supporting the roller 27, namely, a supporting member bent into a .].-shape, 29 a supporting post for pivotably supporting the supporting member 28, and 30 shown in FIGS. 16 and 17 denotes a spring for urging the supporting member 28 so that the roller 27 may come into contact with the concave portion 8 and convex portion 9.
The supporting member 28 is formed of metal and has a hole 32a into which a metal shaft 31 of the roller is rotatably inserted as shown in FIG. 18.
In the optica1 rotary encoder constructed as described above, in the set state, the inner shaft 4 of the first code plate 2 and the outer shaft 5 of the second code plate 3 shown in FIG. 15 are inserted into the hole 26 of the circuit substrate 25 through the through-hole 21 of the slider 20, the pin 2 is brought into engagement with the end 24 of the grooved cam 15, the roller 27 is brought into contact with the concave portion 8 of the first code plate 2 by the force of the spring 30 as shown in FIG. 17, the whole body is covered with the cover 1, and the first window 10, the second window 11 and the reflecting window 12 of the second code plate 3 are positioned so as to oppose to the first, the second and third light receiving and emitting elements 16, 17 and 18, respectively. When the light is projected, in the said set state, from the first, the second and the third elements 16, 17 and 18 toward the second code plate 3 and the first code plate 2 to rotate the inner shaft 4 to rotate the first code plate 2, the second code plate 3 is maintained still since the pin 22 engages with the end 24 of the grooved cam 15. Thereby the projected light of the third element 18 is reflected by the reflecting window 12 of the second code plate 3, and the reflected light is incident upon the third element 18 to release a high level signal from the third element 18. The projected light from the first element 16 and the second element 17 is applied to the reflecting portion 6 or non-reflecting portion 7 of the first code plate 2 through the first window 10 and the second window 11. The reflected light from the reflecting portion 6 is received and the pulse signals are output from the first element 16 and the second element 17. It is noted that the first element 16 and the second element 17 are arranged so that pulse signals different in phase from each other are output from the first element 16 and the second element 17. The operation is repeatedly carried out in which the roller 27 slides over the convex portion 9 of the first code plate 2 into engagement with the concave portion 8 while the first code plate 2 is being rotated, thereby obtaining a clicking feel.
Conversely, in the state wherein the first code plate 2 is maintained still, when the outer shaft 5 is rotated against the force of the spring 23 shown in FIG. 16 to rotate the second code plate 3, the reflecting window 12 of the second code plate 3 moves from the third element 18, whereby the projected light of the third element 18 is not reflected and a low level signal is output from the third element 18. The rotation of the second code plate 3 causes the projected light of the first element 16 and the second element 17 to be applied to the reflecting portion 13 or non-reflecting portion 14 of the second code plate 3. The reflected light from the reflecting portion 13 is received and pulse signals are output from the first element 16 and the second element 17.
In this way, according to the optical rotary encoder, the inner shaft 4 or the outer shaft 5 is rotated to selectively rotate the first code plate 2 and the second code plate 3, thereby enabling to output separate pulse signals.
The conventional optical rotary encoders constructed as described above have various problems as noted below.
According to the first apparatus which needs to be improved, as shown in FIG. 14, the distance a between the surface of the reflecting portion 5 of the first code plate A and the surface of the reflecting portion 9 of the second code plate B is the sum of a thickness a.sub.1 of the metal plate 3 of the code plate A and a distance a.sub.2 between the reverse side of the metal plate 3 and the surface of the metal plate 6 of the second code plate B. Thus, since the thickness a.sub.1 of the metal plate 3 is added, the distance between both the surfaces of the reflecting portions 5 and 9 increases. Accordingly, there is a problem that the light detection characteristic of the element 2 is different between the two code p1ates A and B. To cope with this, the thickness a.sub.1 of the metal plate 3 of the code plate A can be made thinner, in which case, however, there is a problem in that the metal plate 3 loses its rigidity and affects the reflection of light.
A further drawback is the high cost because the pattern composed of the reflecting portions 5, 9 and the non-reflecting portions 6, 10 of the light receiving surfaces of both the code plates A and B is formed by printing the shield coatings 4, 8 on the metal plates 3 and 7.